limestone, sedimentary rock wholly or in large part composed of calcium carbonate. It is ordinarily white but may be colored by impurities, iron oxide making it brown, yellow, or red and carbon making it blue, black, or gray. The texture varies from coarse to fine. Most limestones are formed by the deposition and consolidation of the skeletons of marine invertebrates; a few originate in chemical precipitation from solution. Limestone deposits are frequently of great thickness. The action of organic acids on underground deposits causes such formations as the Luray Caverns, the Carlsbad Caverns, and Mammoth Cave. Limestone is used as a flux in the extraction of iron, as an ingredient in Portland cement, as a source of lime (see calcium oxide calcium oxide, chemical compound, CaO, a colorless, cubic crystalline or white amorphous substance. It is also called lime, quicklime, or caustic lime, but commercial lime often contains impurities, e.g., silica, iron, alumina, and magnesia.
..... Click the link for more information. ), as a building stone, and for ornamentation. Among the important varieties of limestone are marl marl or bog lime, soil, essentially clay mixed with carbonate of lime, highly valued as a dressing or fertilizer. It crumbles rapidly and easily. Marl in which the lime is in the form of invertebrate shells is called shell marl.
..... Click the link for more information. , chalk chalk, mineral of calcium carbonate , similar in composition to limestone, but softer. It is characteristically a marine formation and sometimes occurs in great thickness; the chief constituents of these chalk deposits are the shells of minute animals called
..... Click the link for more information. , oolite oolite (ō`əlīt, ō`ō–)
..... Click the link for more information. , travertine travertine (trăv`ərtĭn, –tēn), form of massive calcium carbonate, CaCO₃
..... Click the link for more information. , dolomite 1 Mineral, calcium magnesium carbonate, CaMg (CO₃)₂. It is commonly crystalline and is white, gray, brown, or reddish in color with a vitreous to pearly luster. The magnesium is sometimes replaced in part by iron or manganese.
..... Click the link for more information. , and marble marble, metamorphic rock composed wholly or in large part of calcite or dolomite crystals, the crystalline texture being the result of metamorphism of limestone by heat and pressure.
..... Click the link for more information. .

limestone

Sedimentary rock composed mainly of calcium carbonate (CaCO₃), usually in the form of calcite and, less commonly, aragonite. It may contain considerable amounts of magnesium carbonate (dolomite) as well. Most limestones have a granular texture; in many cases, the grains are tiny fragments of fossil animal shells. Much knowledge of the Earth's history has been derived from the study of fossils embedded in limestone and other carbonate rocks. Limestone is used as a soil conditioner, in the manufacture of glass, and in agriculture. Ornamental varieties are used for flooring, exterior and interior facings of buildings, and monuments.

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limestone

limestone